This invention concerns automobile bumpers and more particularly safety bumpers which are designed to reduce impact injuries to pedestrians struck by the bumper in an accident. It has heretofore been proposed to interpose an energy absorber in a clearance space between a back up bumper beam and a molded plastic fascia which allows the fascia to move back towards the bumper beam to crush the energy absorber, gradually absorbing the impact of the fascia with a pedestrian to greatly reduce the peak force of impact on a pedestrian's leg or other body part.
However, the clearance space available for accommodating this back movement or deflection of the fascia is quite limited. Crushable structures such as foam or structures with deformable features such as egg crate or cone constructions which have heretofore proposed are slow to begin to absorb energy, i.e., they do not offer much resistance to deformation in the initial movement.
Additionally, these structures tend to “stack up” quickly, that is to reach a point where deformation can only continue under very high crush loads.
Thus, utilization of the available space for energy absorption of such energy absorbers has been poor and have not offered good performance.
Another disadvantage is that these prior proposed absorbers are not easily “tunable”, i.e., able to be modified to produce a particular desired energy dissipation curve or a desired impact force versus crush distance relationship.
Accordingly, it is an object of the present invention to provide an automobile bumper assembly having an impact safety feature which very efficiently uses a small clearance space between a bumper fascia and bumper beam to be effective in energy absorption.
It is an additional object to provide such a safety feature which can be easily tuned to create any desired energy dissipation characteristic.